To update your Urban Terror 4.2, simply run the UrTUpdater, follow the onscreen instructions. and it should automatically update your game to the latest version.

WARNING Make sure you use the updater to download the zUrT42_0009.pk3, zUrT42_0010.pk3 and zUrT42_0011.pk3 because these have been changed since 4.2.003. The updater will overwrite these pk3's with the newer versions.